T-Mobile and MLB Advanced Media also are working on other ways to improve digital content for smartphones and tablets. Mike Sievert, chief marketing officer for T-Mobile USA Inc., says digital consumption in baseball is strong and "today's baseball fan is technologically savvy and data hungry."
I guess I understand that, the MLB is trying to entice the younger, tech-savvy generation to a lifetime of baseball fandom (the MLB FanCave is proof of this) and they have probably been successful. T-Mobile also knows that quite a few fans watch MLB.tv on their cellphones, so being able to advertise their unlimited data service that would work with MLB.tv streaming is a good idea.
However in spite of this, REALLY? A lot of baseball has to do with tradition, and cellphones aren't part of that tradition. I really hope the Nats don't transfer over but we'll see. Seeing cellphones in the bullpen at Fenway Park or any equally old/traditional park would be stupid... It makes much more sense in football where communications with QBs is wireless.
Good article on this topic: http://www.fangraphs.com/blogs/index.php/mlb-announces-bullpen-cell-phones/